Electrical stimulation of physiologic tissue is common in medical practice. In particular, neural stimulation is a strong component of neurology/neurodiagnostics. This stimulation may be accomplished from skin surface stimulation, commonly called cutaneous stimulation or from direct nerve stimulation on exposed neural tissue when direct access to the nerve or brain tissue is available as is sometimes the case in surgery. The technique of electrically stimulating tissue is not without challenges. Two such challenges are electrical stimulus artifact and patient pain.
Electrical stimulus artifact occurs when current from the electrical stimulation electrode attachments flows in undesirable directions through tissue. For example, during stimulation of a nerve axon for purposes of depolarizing the nerve, the desired path for electrical current to flow would be from the attachment electrode cathode into tissue, through the desired nerve and back to the attachment electrode anode. In the ideal world, 100 percent of the delivered stimulating current would flow in this path without any current following alternate, undesirable pathways. However, in the real word, such ideal conditions do not occur and the delivered stimulating current flows in alternative, undesirable paths from anode to cathode in addition to the desired path through the targeted neural tissue. When these alternative, undesirable current pathways intersect with electrical recording activity, the result is the phenomena known as electrical stimulus artifact.
Electrical tissue stimulation can cause significant discomfort in the conscious patient. The pain results from the stimulation current activating tissue pain receptors. In order to minimize patient pain, it is desirable to activate the targeted neural (or other) tissue with the smallest possible delivered current while still facilitating the desired result in the targeted neural activation.